80 bit floating point emulation

[Bruce Carneal]

On Saturday, 9 July 2022 at 06:56:25 UTC, Daniel N wrote:
> On Saturday, 9 July 2022 at 00:05:07 UTC, Adam D Ruppe wrote:
>> On Friday, 8 July 2022 at 22:04:38 UTC, Walter Bright wrote:
>>> In order for DMD to become a proper cross compiler
>>>
>>>
>>> (We don't use other peoples' emulators because of licensing 
>>> issues.)
>>
>> Does ldc have an emulator you don't use for licensing? or does 
>> it manage to be a usable cross compiler without 80 bit reals?
>
> LDC always uses 64-bit double for real, no 80 bit support 
> anywhere afaik.

A quick scan of LLVM code reveals support for a small menagerie 
of floating point types: f16, bf16, f32, f64, f128 and f80 for 
x86 targets.

I imagine LDC could support code generation for any subset of 
these relatively easily.  I'd be surprised if gdc could not.

Which of these types should be supported at CT is an open 
question.  I'd suggest all of them or just {f32, f64}.

A related question is how we might improve multi-target 
programming.  Standardized introspection wrt target HW 
capabilities would be a good first step.  There are others.